The goals of this project are to: (1)\elucidate those molecular mechanisms involved in ATP synthesis in normal liver cells; (2)\understand how ATP synthesis is regulated in liver cells; and (3)\understand why many rapidly growing cancer cells, particularly hepatomas, have an abnormal energy metabolism. To meet these objectives, we are working with the mitochondrial ATP synthetase complex (H+-translocating ATPase) and its ATPase peptide inhibitor. We are studying the F1-component of the ATP synthetase complex in great detail in order to ascertain both its mechanism of action and its structure. Active site studies with covalent labeling agents and X-ray crystallographic studies are being vigorously pursued. Very significantly, we have just elucidated the three-dimensional structure of the F1-ATPase to 9 Angstrom resolution. This is a major advance in understanding how both normal cells and cancer cells synthesize ATP, the energy source essential for supporting growth. Another major advance made on this project within the past two years is the elucidation of how the ATP synthetase molecule is actually regulated by the ATPase peptide inhibitor. Current studies are under way to resolve the structure of the ATP synthetase molecule to 3.5 Angstrom resolution and to understand better how the molecule is regulated in both normal and cancer cells. The studies are both necessary and fundamental to elucidating and understanding the complex mechanisms underlying energy metabolism of normal and cancer cells. (E)